1. Technical Field
The invention relates generally to devices for regulating flow in oil and gas wells. More specifically, the invention relates to a downhole adjustable choke which is suited for metering of well fluid.
2. Background Art
In a multi-zone production well, it is often desirable to produce well fluid over a range of flow rates from different production zones. This flow control may be achieved through a downhole adjustable choke in each production zone. Typically, the downhole adjustable choke includes an orifice with a flow area that can be suitably adjusted to achieve different flow rates. This orifice is typically provided by a tapered plug which extends into a tapered valve seat. The flow area of the orifice is increased or decreased by moving the tapered plug relative to the tapered valve seat. When the tapered plug tightly engages the tapered valve seat, flow through the orifice is prevented. The downhole adjustable choke, however, operates in the presence of highly corrosive fluids and solid particles which can erode the tapered plug and/or valve seat such that the tapered plug can no longer tightly engage the tapered valve seat or the condition of the flow through the orifice is undesirably altered. In such a situation, the tapered plug and/or valve seat will need to be replaced to allow the adjustable choke to function properly. This valve-seat replacement operation is generally time consuming and expensive and may need to be repeated frequently to ensure that flow is properly controlled.
The invention is a downhole adjustable choke which comprises a choke body that is adapted to be lowered into a borehole. The choke body has a bore and an orifice connected to the bore. A sleeve is disposed inside the bore of the choke body. The sleeve has an orifice which is aligned with the orifice in the choke body. A flow plug is movably disposed inside the sleeve. An actuator coupled to the flow plug moves the flow plug relative to the sleeve so that the flow area of the orifice in the sleeve is adjustable.